Not the assassin, but getting closer with the dragon.

A dragon? An assassin? 

Ah, you thought of the other one... I'll give a hint, it uses the first 3 lines, but different, its from a video game.

A human~

As a baby you crawl. An adult, upright, then when your old; walking stick. Then you die, then 'fly'.

Or I could be totally wrong.